Since the degree of integration of almost all highly integrated semiconductor devices having high capacities, such as DRAMs or FRAMs, is doubled every year, the degree of difficulty encountered in semiconductor manufacturing processes is further increasing.
In particular, since a design rule required for a pattern formation process for use in the formation of fine pattern becomes small, it is important to suppress variations in notching or critical dimensions generated during the pattern formation process.
To this end, an anti-reflective film having a low refractive index should be deposited on a bottom film which is to be patterned, to minimize the irregular reflection or diffraction of radiated light of 365 nm or 248 nm. Such an anti-reflective film is exemplified by a nitrided-oxide film, such as SiON. However, the nitrided-oxide film suffers because it causes defects and entails complicated processes. Therefore, there is need for a novel anti-reflective film. From this point of view, an amorphous carbon anti-reflective film is advantageous because it can be inexpensively used for an actual process and be simply manufactured, with excellent applicability.
Although an organic carbon anti-reflective film for realization of high etching selectivity has been typically used as a bottom anti-reflective coating (BARC), which is removed along with a photo-resist, it presently serves as a hard mask upon etching of an oxide film by rather decreasing the selectivity. This is because a general photo-resist has a soft polymer structure, whereas the amorphous carbon anti-reflective film has an sp3 structure as a dense three-dimensional network structure and a planar sp2 structure to exhibit high etching resistance.
Hence, techniques for varying the characteristics of such an amorphous carbon film to maintain optical properties and control selectivity are urgently required.
FIG. 1 is a graph showing the variation in optical properties and etching selectivity depending on the deposition temperature of an organic carbon anti-reflective film.
The amorphous organic carbon anti-reflective film is commonly deposited using plasma. As in FIG. 1, when the deposition temperature is increased, it is not easy to increase hardness and an extinction coefficient (k) associated with anti-reflectivity, due to the expanded graphite structure, therefore resulting in delayed actual application of the amorphous organic carbon anti-reflective film to a semiconductor process.